1. Field of the Invention
The invention generally relates to capacitively powered motors and, in particular a speed control for a single phase capacitively powered motor which maintains the motor speed at a preselected value.
2. Description of the Prior Art
In order to keep manufacturing costs of low cost capacitive motors to a minimum, the control circuit for these low output type of motors uses an input capacitor to lower the input voltage, and to set the power to the motor at a given voltage and frequency. The setting of the power at a given voltage and frequency allows some of the control failure modes to be impedance protected which simplifies the circuit and reduces its costs. This also avoids the need for commercial thermal fuses in order to protect certain failure modes.
One disadvantage to setting the power applied to the motor at a certain level is that the motor speed will vary depending on environmental conditions and, in particular, depending on the resistance to rotation which the motor encounters. There is a need for a low output, low cost capacitively powered motor which operates at a constant or near constant speed.